AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) A submersible 'Jiaolong' works at a depth of 7,062 metres on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached the depth during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) A submersible 'Jiaolong' works at a depth of 7,062 metres on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached the depth during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) A submersible 'Jiaolong' works at a depth of 7,062 metres on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached the depth during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) A submersible 'Jiaolong' works at a depth of 7,062 metres on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached the depth during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 19: (CHINA OUT) Submersible 'Jiaolong' is put into the sea for the second dive during a series of six scheduled ones to attempt the country's deepest-ever 7,000-meter manned dive on June 19, 2012 in At Sea, Unspecified. The submersible 'Jiaolong', carrying three people, reportedly reached a depth of 6,965 meters in the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, on June 19, local time. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 19: (CHINA OUT) Submersible 'Jiaolong' is put into the sea for the second dive during a series of six scheduled ones to attempt the country's deepest-ever 7,000-meter manned dive on June 19, 2012 in At Sea, Unspecified. The submersible 'Jiaolong', carrying three people, reportedly reached a depth of 6,965 meters in the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, on June 19, local time. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) A submersible 'Jiaolong' works at a depth of 7,062 metres on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached the depth during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

QINGDAO, CHINA - JULY 16: (CHINA OUT) Submersible Jiaolong returns from the ocean on Monday, July 16, 2012 om Qingdao, Shandong Province of China. The submersible reached a record depth of 7,062 meters in June in the Mariana Trench in the western Pacific Ocean. Jiaolong returned in glory from a six-week mission to its home port and received new orders for another research dive. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 27: (BEST QUALITY AVAILABLE) (CHINA OUT) Workers take down samples captured from the Mariana Trench on June 27, 2012 in the western Pacific Ocean. The submersible 'Jiaolong', carrying two people, reportedly reached a depth of 7,062 metres during its fifth dive into the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

AT SEA, UNSPECIFIED - JUNE 19: (CHINA OUT) Submersible 'Jiaolong' is taken out of the water after completing the second dive during a series of six scheduled ones to attempt the country's deepest-ever 7,000-meter manned dive on June 19, 2012 in At Sea, Unspecified. The submersible 'Jiaolong', carrying three people, reportedly reached a depth of 6,965 meters in the Mariana Trench, the deepest part of the world's oceans which is located in the western Pacific Ocean, on June 19, local time. (Photo by ChinaFotoPress/ChinaFotoPress via Getty Images)

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"[W]e don't have intact oceanic crust that old ... It would mean that this ocean was formed while Pangea, the last supercontinent, was still in the making," Granot wrote in an email to Business Insider.

To test his hunch that the Mediterranean Sea was hiding something big, Granot conducted four research cruises from October 2012 through October 2014.

A crew towed three large sensors behind a boat, zigzagging across the sea during each trip to hunt for magnetic anomalies — the signatures of magnetic rocks locked in crust that was made by undersea volcanic ridges — buried deep beneath miles of ocean sediment.

"I was shocked," said Granot, who was stuck on a 16-hour flight when he finished processing the data. "The picture was quite clear — I see oceanic crust! Since I had no one to share my new understanding, I had to walk back and forth in the airplane until [we] landed."

The findings could mean the Tethys Ocean formed about 50 million years before scientists thought.

"But we are not sure that it is really part of the Tethys Ocean. It could be that this oceanic crust is not related at all," Granot said, noting that it instead may be part of some other, unknown ocean bottom.

And aside from rewriting textbooks on plate tectonics, Granot says the discovery "could also help to understand heat flow in the eastern Mediterranean, which in turn will help to assess the potential of hydrocarbon [oil and gas reserves] in that region."

Other geologists will likely be working to confirm this finding, and Granot noted in the paper that the different tectonic possibilities that may have generated this discovery should all be tested in future studies.